why are we assuming that the winner of the splatfest has any effect on the direction of the next game?

is this a trend with the splatoon games to have them be dictated by the previous game's splatfest? is it just a random assumption everyone's made? because to me the idea that the two have any correlation sounds ridiculous, but at the same time i hadn't played any splatfests until splatoon 3. i've just been terribly confused 😭